Novel cyclic dimers of perfluorovinyl ethers



United States Patent 2,982,786 Patented May z, 1961-.

r ICC 2,982,786 NOVEL 'CY'CLIC DIMERS or PERFLUOROVINYL Donald Irwin McCane, 'Claymont, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No nrawin File'd Ju'ly 9,1958, S81. No; 147,352

' 6 Claims. romeo-611 The present invention relates to-novelfluorinated cyclic compounds, and more particularly to cyclic derivatives ofalkyl perfluorovinyl ethers.

-=It has'been well-established thatfiuorinated compounds are highly useful gases, liquids and solids due to their inertness and ability towithstand high temperatures.

However, only a very limited number of fluorine com- 7 pounds are commercially available since these compounds are generally diificult and costly to prepare. The present invention resulted from research directedrtowa'rds the discovery. of compounds which possess outstanding solvent powers as well as high temperature resi-stanceandsta bility,-and-which can be readily, and therefore economically, prepared.

It is therefore an objective of the present invention to prepare fluorinated solvents. It is another objective of the present invention to prepare highly fiuorinated liquids which are stable over a wide range of temperatures. Other objectives will become apparent hereinafter.

In accordance with the presentinvention there is provided a new class of fluorinated cyclic compounds having the formula C F (OR) where R is an alkyl group or a fluoroalkyl group. structurally the compounds of the present invention are compounds containing a perfluoro cyclobutane ring to which two alkoxy groups or fluoroalkoxy groups are attached, said alkoxy groups being attached to adjacent carbon atoms.

The alkoxy-perfluorocyclobutanes and fiuoroalkoxy V invention are preferably those having from 1 to 5 carbon atoms in the alkoxy radical. Examples of the alkyland fluoroalkyl perfluorovinyl ethers are methyl perfluorovinyl ether, ethyl perfluorovinyl ether, n-propyl perfluorovinyl ether, n-butyl perfluorovinyl ether, trifluoromethyl in the reaction system when the tetrafluoroethylene is added; otherwise, the'saturated ether, ROC-F2-CF2H, is formed.

The fiuorinated alkyl ethers may be prepared by the reaction of fluorinated alcoholates-with tetrafluoroethylene or by the fiuo'rination of 2-alkoxy propionic acids followed by the decarboxylation anddefluorination of the sodium salt of the perfluorinated Z-alkoxy propionic-acid which leads to the formation of the perfluorinate'd alkyl vinyl ether.

The preparation of the alkyl perfluorovinyl ethers is illustrated by the following experimental procedure.

Into a glass vessel was charged 18.5 g. of n-butyl alcohol dissolved-in 150 ml. of sodium dried dioxane. An excess of the theoretical amount of sodium in the form of a 50% dispersion in xylene was added'with stirring under nitrogen over a period of 4 hours. The

mixture was allowed to stir for an additional 12 hours and then was charged into a 320 ml; stainless steel'bomb; The bomb was sealed, pressured to 300 psi. with tetrafiuoroethylene, and heated to to C. under agitation. The bomb was repressured with tetrailuoroethylene as was necessary to maintain the pressure. The reaction was continued for approximately 2 hours, untilno further decrease in pressure occurred. On removal from the cooled reaction vessel, the reaction mixture was treated with n-butyl alcohol to destroy anyexcess sodium present. The reaction mixture was filtered and the filtrate was distilled. There was obtained 10.1 g. of pure n-butyl perfluorovinyl'ether. a

The present invention. is further illustrated by the following examples.

Example I Into a thick-walled Pyrex combustion tube was charged under nitrogen 20 g. of n-propyl trifluorovinyl ether. The tube was then heated in a combustion furnace at C. for 15 hours. The resulting cooled liquid product was distilled through a 12 inch spinning band column.

A'liquid product having a boiling point at 58.5 to 595 C. I

at 10 mm. was isolated. This product gave a negative test for unsaturation with potassium permanganate. The

yield of the product was 5 g. An infrared spectrographof a sample of this product revealed the complete (lisappearance of the 5.46 micron band found in the vinyl ether. Nuclear magnetic resonance analysis indicated that the structure of the compound was consistent with the l,2-di(n-propoxy)perfiuorocyclobutane.

Analysis.-Calculated for c n o r i c, 4235,11,

5.04; F, 40.68; M.W., 280. Found: (3,; 41.9,- H, 4.9; 5.1;

' F, 40.0; M.W., 290.

. perfluorovinyl ether, and 2,2,2-trifluoroethyl perfluoro- I 7 vinyl ether. The alkyl perfluorovinyl ethers are pr epared ,bythereaction of the alkali metal alcoholate'of the alcohol corresponding to the alkoxy group in the ether RONa+CF =CF- ROCF- CF-,,+NaF It is not necessary that the alkali metal alcoholate be isolated/the reaction may be carried out byreacting the alcohol with a sodium dispersion 'in'an organic solvent and then" adding tetraflu'or oethylene a; the resultin g reaction mixture. However, greatcare'should be takenfthat no hydroxyl hydrogen or other active hydrogen remains"- with tetrafluoroethylene. The reaction may be illustrated by thefollowing equation? I Y a Example II Using the procedure of Example I, 20.5 g. of n-bu-tyl perfluorovinyl ether was dimerized. There was obtained.

on work-up of the product 12.0 g. of starting material and 4.4 g. of the dimer of n-butyl perfluoro-vinyl ether. a The 1,2-di(n-butoxy)perfluoroeyclobutane was found to have a boiling point at 44 C; at a pressure of 2 mm. The density of the liquid was 1.19. The refractive index of the liquid'was measured to-be"1.3713 at 25 C.v

Analysisr calculated for 0 11 0 1 0, 46.75 H,

5.88; F, 36.98; M.W., 308.. Found: C, 45.4; H, 5.7;} I

F, 35.8; M.W., 304.

Example III I Into each of 4 Carius tubes was charged under nitrogen 50 g. of methyl trifluorovinyl' ether, 0.5 g. of phefnothiazinc and 6 drops of TerpenefB, a commercially'avaiL. able polymerization inhibitor comprisingterpene hydrov carbons. Y'Ihe sealed tubes were heated to C. to; V

l2 hours. Distillationof the combined products gave 166 3 ing a boiling point at 119-121 C. at atmospheric pressure.

Example IV Employing the procedure of Example I, 14.0 :g. of 2,2,2-trifluoroethyl perfiuorovinyl ether was dimerized in the presence of 0.2 g. of phenothiazine and 6 drops of Terpene B. There was obtained on work-up of the reaction mixture 7.6 g. of starting material and g. of 1,2-di(2',2',2-trifluoroethoxy) perfiuorocyclobutane having a boiling point at 156 to 157 C., a refractive index at 25 C. of about 1.3185 and a density of 1.68 g./cm.

The examples hereinabove have illustrated the preparamedia. These solvents may further be used as hydraulic fluidsand lubricants, particularly at elevated temperation of the 1,2-di(alkoxy)perfluorocyclobutanes of the present invention. The 1,2di(alkoxy)perfluorocyclobutanes of the present invention may exist as cisand trans-isomers. However, since isomers aredifiicult to separate and have the same properties, it is customary to consider the isomers as a single compound.

Various modifications of the process for the preparation.

of these compounds will occur to those skilled in the art. Thus, although not essential, the 1,2-di(alkoxy)perfiuorocyclobutanes may be prepared in the presence of a solvent. In general, it is greatly preferred to prepare the l,2-di(alkoxy)perfluorocyclobutane in the presence of known polymerization inhibitors, since the alkyl perfluorovinyl ethers have a great tendency to polymerize to linear polymers in the presence of even the smallest quantities of oxygen. 7

The 1,2-di(alkoxy)perfluorocyclobutanes of the present invention possess outstanding high temperature stability. They may be heated at 500 to600 C. for long periods of time without decomposition. These comtures. Due to their cyclic and ether structure, the 1,2-di- (alkoxy)perfluorocryclobutane are also highly useful solvents for fluorinated and unfluorinated compounds. The compounds of the prescntinvention may be further employed as chemical intermediates.

I I claim;

1. A 1,2-di(alkoxy)perfluorocyclobutane having the formula 'orron on where Risa member of the class consisting of alkyl and fiuoroalkyl radicals. u Y

2. 1,2-di(methoxy)perfluorocyclobutane.

4. 1,2-di(n-propoxy)perfluorocyclobutane.

5. 1,2-di(n-butoxy)perfluorocyclobutane.

6. The process for'preparing .1, 2-di(a1koxy)perfluorocyclobutane which comprises heating in an inert atmosphere and in the absence of a polymerization initiator, an

pounds are therefore exceedingly useful as heat transfer my.

alkyl perfiuorovinyl ether having the formula CF =CFOR wherein R is a member of the class consisting of alkyl and fluoroalkyl radicals, to a temperature of to 350 C. N v References Cited in the tile of this patent 1 Coifman et al.: Iour. Amer. Chem. Soc., vol. 71 (1949), pages 490-96 (7 pages). Barr et al.: .Tour. Amer. Chem.

Soc., vol. 72 (1950). pages 4480- 82 (3 pages). l 

1. A 1,2-DI(ALKOXY)PERFLUOROCYCLOBUTANE HAVING THE FORMULA 